Building up plant defenses by breaking down proteins

The levels of proteins in plants are regulated at all stages of the plant life cycle. In addition to protein synthesis, increasing attention is drawn to protein degradation thereby focusing on the proteolytic pathway involving the ubiquitination of target proteins for subsequent degradation by the 26S proteasome (Ub/26S). Increasing evidence has been gathered in the past decade for the role of proteolysis in plant defense. This manuscript briefly reviews the main components of the ubiquitination pathway, with focus on E3 ubiquitin ligases, and their involvement in the different disease resistance mechanisms. It can be concluded that E3 ubiquitin ligases are involved in different defense responses including gene-for-gene resistance, early defense reactions and induced disease resistance.